The use of wireless communication systems is growing with users now numbering well into the millions. One of the most popular wireless communications systems is the cellular telephone, consisting of a mobile station (or handset) and a base station. Cellular telephones allow a user to talk over the telephone without having to remain in a fixed location. This allows users to, for example, move freely about the community while talking on the phone.
The wireless communication systems may communicate using the Code Division Multiple Access (CDMA) standard. CDMA is a communication standard permitting mobile users of wireless communication devices to exchange data over a telephone system wherein radio signals carry data to and from the wireless devices. A set of standards that define a version of CDMA that is particularly suitable for use with the invention include IS95, IS-95A, and IS-95B, Mobile Station-Base Station Compatibility Standard for Dual-Mode Spread Spectrum Systems; TIA/EIA/IS-2000-2, Physical Layer Standard for cdma2000 Spread Spectrum Systems; and TIA/EIA/IS-2000-5 Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems, all of which are herein incorporated by reference in their entirety.
CDMA call processing decisions are largely dependent on forward and reverse link signal conditions. For example, a soft-handoff requires that the mobile select pilots that, as a set, will be usable for maintaining a communications link with the base station in the short term. There is, therefore, significant value in being able to predict signal conditions in the short-term in order to make better call processing decisions.
Pilot strengths are often, if not generally, predictable in the short-term. If reliable pilot strength predictions were available, mobile station or base station call processing could use the predictions to make informed decisions such as which pilot(s) to handoff to so that the frame error rate is maintained low and system capacity is minimally impacted.
While an estimate of a pilot's phase rate gives an indication of the velocity component of the mobile in the direction of the signal path from the base station, it may not consistently give a good indication of the expected change in pilot strength from that base station. In order to judge the usefulness of such estimates of phase rates in real-time, the mobile can use an integrity indicator.